Distortion-measuring system



Nov. 30 1926. 1,608,546

A. B. CLARK ET Al.

DIsToRTIoN MEASUMNQ SYSTEM v Filed May 10, 1923 I 'EN TORS ,x TTORNEYPatented Nov. 30, 1926.

ALVA B. CLARK, OF BROOKLYN,

AND ROY B. SHANCK, OF WOODSIDE, NEW YORK, AS-

SIGNORS TO AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A CORPORATION F NEW YORK.

DISTORTION-MEASURING SYSTEM.

Application filed nay 1c. 192s. serial No. 638,123.

This invention relates to electrical measuring systems and particularlyto means for determining the existence and the magnitude ofdistortion oftelegraph signaling impulses produced in the course of transmitting thesaid impulses between two stations upon the same line.

In the transmission of telegraph signals. each made up of a plurality ofimpulses, and each impulse having a` definite lengtl distortion of theimpulses and therefore of the signals) may be produced by various causesinherent in the line or in the apparatus connected therewith or both.The distortion with which this invention is con- .cerned manifestsitself in lengthening or shortening the duration of the impulses whichconstitute the. signal transmitted over the line. This lengthening orshortening of the duration of the impulse interferes with the properrecording of the signals atany station connected with the said line andconsequently impairs the efficiency of transmission. y

Various systems for determining the existence and the magnitude of thisform of distortion have been devised and used, but, due either to the.complexity of the apparatus required or to other causes, they have notbeen Widely used. VOne such method consists in the use of a l/Vheatstonetape recorder connected with the receiving end of a line. to whichperfect signals are applied at the sending end for the purpose ofrecording the said signals at the receiving end. The tape records ofthese signals are then measured whereby any distortion and the magnitudethereof may be determined.` This method, however, is quite laborious andeX- pensive. Other ways employed heretofore indicate only averagedistortion.

. it is the object of this invention to provide simple means forindicating the existence of distortion of the signaling impulses and formeasuring the magnitude of the same.

This invention will be clearly understood from the following descriptionwhen read in connection withthe attached drawing, of which Figure lshowsschematically an ar rangement embodying the invention and Fig. lashows graphical-ly two signal characters each comprising live impulses,which :ligure will assist inunderstanding the nature tue invention.

In Fig. "l, A represents a station from which signalling impulses may beapplied to the line Ll extending between station A and station B, Thetransmitting device T1 is intended to represent symbolically any form oftransmitting device such as a tape transmitter, a printing telegraphdistributor or other device by means of which a plurality of impulsesrepresenting signal characters may be applied to the line L1. l),reprecents a differential polarized relay connected with the line L1 andwith the artificial line ALl adapted to balance the real line. For thesake of brevity the details of the apparatus at station A need not befurther described since they form no part of this invention.

The terminal apparatus at which preferably is similar to that at stationA, includes a transmitter T2 and a differential polar relay P2 connectedbetween the line Ll and the artificial line AL2. The armature of relay`P, may be connected through its upper contact with the negative poleofthe battery B2, and the lower contact may remain disconnected. Thisarmature is connected by conductor 16 with the brush 1l 4which isadapted to make contact with the segments of the receiving distributorring D2. The ring, which is shown developedin a straight line in thedrawing, comprises ten conductive segments of equal size and equally`spaced by insulating segments, but as will be apparent from thesubsequent description of this invention, it may comprise any number ofsegments. Each segment is connected with its individual relay of thetrain of rclays designated R, to R1, inclusive. These relays, whichasshown, are of the neutral type, will be Qperatedwhen a current impulseis impressed upon their respective seg-- ments by the brush 1l, and thusin effect store upq for the` purpose of further investi-- gation, thesignal character received at sta tion B. Tt is customary in printirgtclcgraph systems to represent a signal characV ter by a combination of`live impulses, so the segments 1 to 5 and their associated relays arearranged tc receive one signal character and the segments 6 to l0 withtheir asso ciated relays toreceive another and preferably a differentlsignal character. `Since the nature of the invention willbe clearlyunderstood by 'the deecripticn of the inode station B, l

second signal character, which will be applied to the segments 6 to 10inclusive, comprises `a spacing impulse followed by two markingimpulses, which are in turn followed by two spacing impulses. For thesalre o'l' brevity we will describe the operation oit the system for thefirst signal character. The application of the first marl;- ing impulse,viz, anegative impulse, will continue as long as the brush 11 remains incontact with the segment 1 and until the brush is about to enter uponsegment 2. Similarly, the application of the second marking impulse willcontinue throughout the time that the brush 11 remains in contact withsegment 2 and until it is about to move onto segment 3. And, in likemanner, the succeeding impulses will continue as long as the brush 11remains in Contact with the respective segments, assuming, of course,that the said source ot distortionless naling impulses is not only insynchronism but also in phase with the ring D2. As the brush 11 movesover segment 1, current will flow through the winding of the relay R1 toground, thereby effecting the operation ci the said relay, which will belocked-up by eurrentthat flows through a circuit embracing battery B2,the back contact of relay R12, conductor 14.-, upper contact of relay R1and the winding of the said latter relay. y, In similar manner, relay R2will be operated when the brush 11 moves over segment 2 and the saidrelay will be locked-up by current from battery B2.V As the brush 11moves over segment 3, relay R3 will not be energized since the armatureof relay P2 will be on its lower contact with which no source ofpotential is connected. It is desirable to point out that if sources ofopposite polarity were connected with the upper and lower contactsrespectively of relay P2, it would necessitate the use ot polar' relaysin the re-` lay train represented by R1 to Rlo inclusive. F or the sakeof simplicity, neutral relays have been used for this purpose andtherefore a space is represented by the absence of current rather thanby a current impulse et polarity opposite to a marking impulsAccordingly, relay R3 remains unoperated and consequently its armatureis held against its lower Contact by the action of the retractilespring. In like manner, relay R4 remains unouerated durine the assafe ofthe 1 C CJ brush 11 over the segment t and its armature is similarlyheld against its lower contact. Relay will respond to the llowof currentrepresenting a marking impulse during the passage o the brush 11 oversegment 5 and `its armature will be drawn against its upper contact, andthe relay will be locked-up by current from the source B2.

Upon the operation of relay R5, current will flow from the battery B2over a circuit embracing conductor 14:, upper contacts of relays Rl andR2, lower R2 and' R2, upper contact of relay R5 and winding ot' relayR11 to ground, thereby energizing the last relay and causing itsarmature to be held away from its grounded contact. It will, therefore,be seen that relay Ru will not operate unless the circuit through thesaid contacts is closed, which in turn depends upon the operation oitrelays Rl to 2 "Whether relay R11 has operated is determined as follows:l/Vhile the brush 11 is traveling over contacts 6 to 10 inclusive and isthereby storing up the second signal character of Fig. 1, the brush 12,associated with the ring D2, is likewise traveling over segments 6 to 10of ring D2. Vhen the brush 12 makes contact with segment 7', thegrounded source of potential B3 will be applied to the indicating device13. This. however, will not operate it' the armature ot relay R21, withwhich the device 13 is. connected, is held away from its groundedcontact due to the energization of the said relay Rn. The failure ofthis device to operate indicates, of course, that the ring is sooriented while the distortionless signals are being applied to it duringthe process ot' calibration that the relays of the relay train have beenproperly operated to close the circuit ot the alarm control relay R12.Then the brush 12 makes contact with segment 9 the release relay R22will be energized and its armature will be drawn to its right-handcontact, thereby disconnecting the grounded battery B2 from the trainot' relays Rl to R5 inclusive and also from the alarm relay R thusrestoring the system to normal.

In Calibrating the system, it is desired to determine'how tar in eitherdirection oit ro tation, the ring D2 may be oriented betere it fails toproperly transmit to the r '.'s R1 to R5 inclusive the signalingimpulses impressed by the source of distortionlcss signaling impulsesupon the brush 1l, l" the ring D2 is oriented, for example` in thelett-hand direction a point will be reaclmd where, ttor example, aiiegative impulse will be applied to the relay This is denced by thetact that relay R2, which would normally not be energized it lthesignaling impulses were properly centered. will now be energized by theHow of current therethrough. Accordingly, its armature will contacts otrelays be attracted to its upper Contact and loclred in that position,`and consequently the circuit embracing battery B2 conductor lland thecontacts ol relays R, to R, will be cut olf from relay R2. Accordinglythe alarm control relay R11 will not be energized and its armature willremain upon its grounded contact. Vfhen the brush 12mm-.fes onto segment7 the alarm device 13 will be operated by current flowing therethrough:trom battery B2 to ground. The operation of this device serves toapprisef the person who is making the test that the ring D2 has beenoriented so far in a left-hand direi-tion that the receiving apparatusfails'to receive the Ndistortionless signals being applied to the Vhanddirection until the apparatus fails to properly receive signals, whichwould he indicated yin the manner just described. rilhis latter point isalso noted upon the said ring and the distance between the tivo pointsis known Vas the range of orientation Without failure. @ne-half of thisdistance is commonly known as the niargin for distortiollless signals.

Having determined the margin through which the receiving ring D2 may beoriented before failure when receivingdistortionless signals, thereceiving; apparatus should then be connected effectively to the lineL1. After the yreceiving apparatus has thus been connected it should beadjusted to compensate for the time lag resulting from the transmissionof signals over the said line. This adjustment consists in orienting thering D2 in such direction and to such extent that the brush llrivillbegin to make contact with the segment l When the first impulse of thesignal transmitted over the line L1 from the distant station A is ar-`riving at station B. Since the rings at station B are operated insynchronism Tvith the transmitting apparatus at station A and sincethere is a timelag inthe transmission of a signal from A to B, the brushil will normally `have travelled some distance along the segment lheforeth-e signal transmitted from station A begins to arrive at stationB if the brush l1. began to make Contact with segment l of ring D,2 atthe same time that the armature of the transmitter T1 at station Atouched the. contact point connected with one of the poles of the transmitting battery. The adjustment for time lag consists simply inorienting the ring D2 so that the brush .ll moves over the segment lWhile the signal transmitted from SMOH A arrives at station B.

Having calibrated the distortion measure ing apparatus, that is, havingdetermined its margin for distortionless signals, and furthermore,having adjusted the receiving apparatus for time lag, the nent stepconsists in determining the change in themargin diie to distortion ofsignals received at station liet-.it be assumed that the transmittingapparatus at station A is sending the first signal character shoivn inFig` la, consisting of tivo marking impulses followed by tivo spacingimpulses, which in turn are `followed hy a Vsinglemarking impulse. Y Asing Will be manifested by the operation of the indicating device 13 whenthe ring D2 is oriented. lf the third impulse, which is an open circuitspacing impulse, is appreciahly lengthened, the preceding markingimpulse, which is closed circuit' impulse, will he correspondinglyshortened. To determine the magnitude of this distortion the ring D2should be oriented .in both directions. Since the duration of themarking impulse, which would normally be applied' to the vsegment 2While the brush 6 is in contact therewith, is shortened by thecorresponding lengthening of the succeeding spacing impulse, it Will beapparentl that the ring D2 cannot be oriented as far in onegdirection aswhen distortionless signals are being received before failure occurs,which would be indicated by the alarm bell 13.

rlhe difference between the margin With noV distortion and the marginWith distortion is the measure of he distortion of the signal.

'lher manner of testing the existence of excessive distortation in thesignal character set up hy the relays BG to R10 inclusive by the passageof the brush l1 over t-he segments 6 to 10 is identical with that fortesting the firstr signalcharacter and need not be described in detail.Furthermore, for the sake of simplicity, the indicating device and therelease relay and other equipment asso;- ciated with the relay train BGto B10 have not been shoivn since such apparatus and its mode ofconnection would he similar to that shown and 'described in connectionWith relays R1 to inclusive. Y

lt is desired to point out that the mode of connection of the armaturesof relays R1 to with the contact points or the armatures of theiradjacent relays depends upon the. arrangement ofthe marking and spacingimpulses constituting the particular signal character intended to bereceived by the train of relays R1 to Thus, for example,

if, instead of the signal character repre-Kv sented by Fig. la, it isdesired to receive'a character in which the first, third and fifthimpulses are of the marking type andthe second and fourth of thespacing'type, the armature of relayfB.1 should be connected With thearmature of relay R2 and the lovver contact of relay R, with the uppercontact of relay B3, the armature of relay R3 With the armature of relayB4, the lower contact of which should be Vconnected with the uppercontact of relay B5. n practice, it is den sii-able to provide avplurality of simple switches whereby the armatures of each relay oli' atrain may readily be connected With the adjacent higher numbered relayin any desired manner. i

In the drawing the length ot the conductive segment of ring D2 is shownas approximately one-half the total length of a conductive and aninsulating' combined. ln practice better results will be obtained if thelength of the conductive segment is small, that is, one-fourth or evenless of the said total length of the conductive and insulating segments.

The form of embodiment of the invention shown in Fig. l is purelyschematic and is not intended to constitute a limitation of the scope ofthe invention. it is desired to point out that While We have shoivn thereceivingapparatus, viz, the. distortion measuring apparatus located ata ditllerent station from that trom which the signals are transmitted,it is to be understood that such distortion measuring apparatus may belocated at the transmitting station, sucli being the custom in makingso-called loop measure-- ments wherein both terminals ot the line areavailable at the. same station. in such case, a printing telegraphdistributor might be used as a transmitter of the signal characters,which distributor would be operated by the same shaft that drives thebrushes ot rings D2 and D.S so that exact synchronism of thetransmitting and receiving apparatus could readily be maintained.

While this invention has been as embodied in a particular rangement ofparts it is to that it is not so limited but is capable of embodiment inother and diil'erent forms Without departing from the spirit and scopeof the appended claims.

What is claimed is:

l. In a distortion measuring system in which a signal comprising aplurality oit electrical impulses is transmitted over a line, thecombination With a. source of current impulses of a line and a receivingdevice comprising means to automatically indicate the magnitude by whichthe distortion of any of said impulses exceeds a predeterminedmagnitude.

2. In a distortion measuring system in which a signal comprising Aaplurality of electrical impulses is transmitted over a line, thecombination with a source of current impulses of a line and a receivingdevice comprising means to indicate automatically the distortion of anyimpulses exceeding a predetermined magnitude and to measure the degreeof the said. distortion.

3. In a distortion measuring system the combination with a line ot atransmitting device adapted to impress upon said line signalingcharacters, each comprising a pluraldisclosed form and arbe understood`ctmnected with said line, and

'of the lengthening or ity ot impulses, and a distortion measuringdevice comprising a train oi" relays connected Witli a segmentaldistributing ring whereby cach relay ot said train may be effectively anindicating system connected with said relays to show Whether distortionot said signal characters exceeds a predetermined limit. Y

4. ln a distortion measuring' system, the combination with a line or' asource of current impulses, a receiving relay responsive to saidimpulses, a segmental distributor having it-s brush connected with thearmature ot said relay whereby open or closed impulses may be applied tosaid distributor depending upon the position of said armature of thereceiving relay, a relay train comprising a plurality of relays, eachindividual to and connected with a segment of said distributor, thearmatures of which relays are connected with certain contacts of thesucceeding relays, the mode of connection depending upon the signalcharacter to be received, a second distributor having a sou ce oipotential connected with the brush thereof and an alarm device connectedwith a predetermined segment thereof, and a relay connected with thearmatures of said relay train to prevent the operation olsaid alarmdevice When the distortion oi the received signal does not exceed apredetermined limit.

5. The method for determining the degree shortening of signal impulsestransmitted by a printing telegraph transmitter over a line to aprinting telegraph receiver, which consists in applying undistortedimpulses to the said receiver and measuring the range through which thereceiving segments may be oriented Without failure, applying undistortedimpulses to the sending end or the said line for transmission thereover,adjusting the receiving segments to compensate for the time lag betweenthe transmission and reception of signal impulses transmitted over thesaid line, measuring the range through which the said receiving segmentsmay be oriented Without failure and determining the magnitude or'distortion by the diiierence between the said second measurement and thesaid tirst measurement.

6. The. method for determining the degree of the lengthening orshortening of signal impulses transmitted by a printing telegraphtransmitter over a line to a printing telegraph receiver, Which consistsin measuring the range of the receiving segments for undistortedsignals, measuring the range of said segments for signals distorted bytransmission over the said line and the magnitude of distortionby thedifference between the second range and the first range.

7. The method for determining the degree of the lengthening orshortening of signal determiningl lli',

impllllesA transmitted* by a printing telegraph transmitter over 2Liinevte printing teiegraph receiver, which consists in adjust-y ing'thereceiving segments Yjor the receptionV iivuridistorted signals,adjusting-for the time lag between transmission and reception ofthesaidvsigrials orlenting the receiving segments in each directionrmtil failure occurs Y May, '1923.

in the reception olf theseid segments, and

producing an alarmV Whenever'the receiver 10 AWA' B. @LAR EL. ROY B.SHANGK.

